It's showing type error

My logic is correct and the program should give correct output.

```
lloyd = {
"name": "Lloyd",
"homework": [90.0, 97.0, 75.0, 92.0],
"quizzes": [88.0, 40.0, 94.0],
"tests": [75.0, 90.0]
}
alice = {
"name": "Alice",
"homework": [100.0, 92.0, 98.0, 100.0],
"quizzes": [82.0, 83.0, 91.0],
"tests": [89.0, 97.0]
}
tyler = {
"name": "Tyler",
"homework": [0.0, 87.0, 75.0, 22.0],
"quizzes": [0.0, 75.0, 78.0],
"tests": [100.0, 100.0]
}
def average(numbers):
total=sum(numbers)# Add your function below!
ave =float(total)/len(numbers)
return ave
def get_average(student):
homework=average(student["homework"])
quizzes=average(student["quizzes"])
tests=average(student["tests"])
return 0.1*homework+0.3*quizzes+0.6*tests
def get_letter_grade(score):
if score>=90:
return "A"
elif score>=80:
return "B"
elif score>=70:
return "C"
elif score>=60:
return "D"
else:
return "F"
get_letter_grade(get_average(lloyd))
def get_class_average(students):
results=[]
for i in students:
results.append(get_average(i))
return average(results)
students=['lloyd','alice','tyler']
print get_class_average(students)
print get_letter_grade(get_class_average(students))
```